Photoluminescence Tuning via Cation Substitution in Oxonitridosilicate Phosphors: DFT Calculations, Different Site Occupations, and Luminescence Mechanisms

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• 作者：Guogang Li ; Chun Che Lin ; Wei-Ting Chen ; Maxim S. Molokeev ; Victor V. Atuchin ; Chang-Yang Chiang ; Wuzong Zhou ; Chin-Wei Wang ; Wen-Hsien Li ; Hwo-Shuenn Sheu ; Ting-Shan Chan ; Chonggeng Ma ; Ru-Shi Liu
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：May 13, 2014
• 年：2014
• 卷：26
• 期：9
• 页码：2991-3001
• 全文大小：706K
• 年卷期：v.26,no.9(May 13, 2014)
• ISSN：1520-5002

文摘

Tuning and optimizing luminescent properties of oxonitridosilicates phosphors are important for white light-emitting diode (WLED) applications. To improve the color rendering index, correlated color temperature and thermal stability of layer-structured MSi₂O₂N₂:Eu (M = Sr, Ba) phosphors, cation substitutions have been used to adjust their luminescent properties. However, the underlying mechanisms are still unclear. In this research, a series of (Sr_1鈥?i>xBa_x)Si₂O₂N₂:Eu (0 鈮?x 鈮?1) compounds were prepared by solid-state reaction, after which systematic emission variations were investigated. The crystal structures of (Sr_1鈥?i>xBa_x)Si₂O₂N₂:Eu (0 鈮?x 鈮?1) are nominally divided into three sections, namely, Phase 1 (0 鈮?x 鈮?0.65), Phase 2 (0.65 < x < 0.80), and Phase 3 (0.80 鈮?x 鈮?1) based on the X-ray diffraction measurements. These experimental results are further confirmed by optimizing the crystal structure data with first-principle calculations. Continuous luminescence adjustments from green to yellow are observed in Phase 1 with gradual replacement of Sr²⁺ with Ba²⁺, and the abnormal redshift is clarified through extended X-ray absorption fine structure analysis. Sr(Eu)鈥揙/N bond length shrinkage in local structure causes the redshift emission, and the corresponding luminescence mechanism is proposed. Controllable luminescence in Phase 2 (from blue to white) and Phase 3 (from cyan to yellowish green) are observed. Based on the high-resolution transmission electron microscopy and selected area electron diffraction analysis, the two kinds of luminescence tuning are attributed to phase segregation. This study serves as a guide in developing oxonitride luminescent materials with controllable optical properties based on variations in local coordination environments through cation substitutions.